US8790264B2ActiveUtilityA1

Vibro-acoustic detection of cardiac conditions

74
Individually held — no corporate assignee on recordPriority: May 27, 2010Filed: May 27, 2011Granted: Jul 29, 2014
Est. expiryMay 27, 2030(~3.8 yrs left)· nominal 20-yr term from priority
Inventors:Richard H. SandlerHansen Mansy
A61B 7/026A61B 6/503A61B 5/021A61B 8/02A61B 5/0205A61B 7/04A61B 5/11A61B 5/318
74
PatentIndex Score
13
Cited by
15
References
49
Claims

Abstract

Apparatus and methods for vibro-acoustic detection of cardiac conditions are disclosed. An example method includes calculating a frequency difference between a first frequency of a first cardiac signal and a second frequency of a second cardiac signal; calculating an amplitude difference between the first cardiac signal and the second cardiac signal; calculating a root-mean-square value based on a difference between the first cardiac signal and the second cardiac signal; calculating a value based on the frequency difference, the amplitude difference, and the root-mean-square value; and detecting a cardiac condition based on the value.

Claims

exact text as granted — not AI-modified
We claim: 
     
       1. A method to detect a cardiac condition, the method comprising:
 calculating, with a processor, a frequency difference between a first frequency of a first cardiac signal and a second frequency of a second cardiac signal, wherein the first and second cardiac signals are vibrocardiography signals; 
 calculating, with the processor, an amplitude difference between the first cardiac signal and the second cardiac signal, wherein calculating the amplitude difference comprises calculating a difference between a first amplitude ratio and a second amplitude ratio; 
 calculating, with the processor, a root-mean-square value based on a difference between the first cardiac signal and the second cardiac signal; 
 calculating, with the processor, a value based on the frequency difference, the amplitude difference, and the root-mean-square value; and 
 detecting a cardiac condition based on the value. 
 
     
     
       2. The method as described in  claim 1 , further comprising calculating the first amplitude ratio and the second amplitude ratio using respective J, H and I peaks of the respective first and second cardiac signals. 
     
     
       3. The method as described in  claim 2 , wherein calculating the first amplitude ratio comprises:
 calculating a first difference between an amplitude of a J peak of the first cardiac signal and an amplitude of an I peak of the first cardiac signal; 
 calculating a second difference between the amplitude of the I peak of the first cardiac signal and an amplitude of an H peak of the first cardiac signal; and 
 dividing the first difference by the second difference. 
 
     
     
       4. The method as described in  claim 2 , wherein calculating the second amplitude ratio comprises:
 calculating a third difference between an amplitude of a J peak of the second cardiac signal and an amplitude of an I peak of the second cardiac signal; 
 calculating a fourth difference between an amplitude of the I peak of the second cardiac signal and an amplitude of an H peak of the second cardiac signal; and 
 dividing the third difference by the fourth difference. 
 
     
     
       5. The method as described in  claim 1 , further comprising normalizing the amplitude difference. 
     
     
       6. The method as described in  claim 1 , further comprising:
 normalizing the first cardiac signal by an amplitude of a J peak of the first cardiac signal to form a first normalized cardiac signal; 
 normalizing the second cardiac signal by an amplitude of a J peak of the second cardiac signal to form a second normalized cardiac signal; and 
 calculating the root-mean-square value based on the difference between the first cardiac signal and the second cardiac signal by calculating a difference between the first normalized cardiac signal and the second normalized cardiac signal. 
 
     
     
       7. The method as described in  claim 1 , further comprising temporally aligning the first cardiac signal and the second cardiac signal prior to calculating the root-mean-square value. 
     
     
       8. The method as described in  claim 7 , wherein temporally aligning the first cardiac signal and the second cardiac signal comprises using a J peak of the first cardiac signal and a J peak of the second cardiac signal. 
     
     
       9. The method as described in  claim 1 , wherein the first frequency of the first cardiac signal is an instantaneous frequency adjacent a J peak of the first cardiac signal. 
     
     
       10. The method as described in  claim 9 , further comprising calculating the instantaneous frequency using a Hilbert transform. 
     
     
       11. The method as described in  claim 1 , wherein detecting the cardiac condition based on the value comprises comparing the value to a threshold associated with a heart condition. 
     
     
       12. The method as described in  claim 1 , wherein the first cardiac signal is indicative of a first breathing phase and the second cardiac signal is indicative of a second breathing phase. 
     
     
       13. The method as described in  claim 12 , wherein the first breathing phase is an inspiratory phase and the second breathing phase is an expiratory phase. 
     
     
       14. The method as described in  claim 12 , wherein the first breathing phase is an inspiratory phase and the second breathing phase is an inspiratory phase. 
     
     
       15. The method as described in  claim 1 , wherein the first cardiac signal is a mean of a received cardiac signal. 
     
     
       16. The method as described in  claim 15 , wherein determining the mean of the received cardiac signal comprises sampling a plurality of cardiac cycles. 
     
     
       17. The method as described in  claim 1 , wherein:
 the second cardiac signal is indicative of a sequential cardiac cycle after the first cardiac signal; and 
 the value represents a beat-to-beat variability. 
 
     
     
       18. The method as described in  claim 1 , wherein the cardiac signals are acquired from a patient involved in an activity. 
     
     
       19. The method as described in  claim 18 , wherein the activity is standing. 
     
     
       20. The method as described in  claim 18 , wherein the activity is a valsalva maneuver. 
     
     
       21. The method as described in  claim 1 , wherein calculating the at least one of the frequency difference and the amplitude difference comprises performing a time-frequency analysis. 
     
     
       22. The method as described in  claim 1 , wherein the first cardiac signal is measured at a first location of a patient and the second cardiac signal is measured at a second location of the patient different than the first location. 
     
     
       23. The method as described in  claim 1 , wherein the first cardiac signal is received at a first time and the second cardiac signal is received at a second time different from the first time. 
     
     
       24. The method as described in  claim 23 , wherein a difference between the first time and the second time is greater than one hour. 
     
     
       25. A method to detect a cardiac condition, the method comprising:
 calculating, with a processor, a frequency difference between a first frequency of a first cardiac signal and a second frequency of a second cardiac signal, wherein the first and second cardiac signals are vibrocardiography signals; 
 calculating, with the processor, an amplitude difference between the first cardiac signal and the second cardiac signal; 
 calculating, with the processor, a root-mean-square value based on a difference between the first cardiac signal and the second cardiac signal; 
 calculating, with the processor, a value based on the frequency difference, the amplitude difference, and the root-mean-square value, wherein calculating the value comprises calculating a sum of squares of the frequency difference, the amplitude difference, and the root-mean-square value; and 
 detecting a cardiac condition based on the value. 
 
     
     
       26. The method as described in  claim 25 , wherein the sum is a weighted sum. 
     
     
       27. A method to detect a cardiac condition, the method comprising:
 receiving an electrocardiographic signal; 
 calculating a time difference between a peak of a first cardiac signal and a peak of the electrocardiographic signal; 
 calculating, with a processor, a frequency difference between a first frequency of the first cardiac signal and a second frequency of a second cardiac signal, wherein the first and second cardiac signals are vibrocardiography signals; 
 calculating, with the processor, an amplitude difference between the first cardiac signal and the second cardiac signal; 
 calculating, with the processor, a root-mean-square value based on a difference between the first cardiac signal and the second cardiac signal; 
 calculating, with the processor, a value based on the frequency difference, the amplitude difference, and the root-mean-square value; and 
 detecting a cardiac condition based on the value. 
 
     
     
       28. A method to detect a cardiac condition, the method comprising:
 receiving an acoustic signal; 
 calculating a time difference between a peak of a first cardiac signal and a peak of the acoustic signal; 
 calculating, with a processor, a frequency difference between a first frequency of the first cardiac signal and a second frequency of a second cardiac signal, wherein the first and second cardiac signals are vibrocardiography signals; 
 calculating, with the processor, an amplitude difference between the first cardiac signal and the second cardiac signal; 
 calculating, with the processor, a root-mean-square value based on a difference between the first cardiac signal and the second cardiac signal; 
 calculating, with the processor, a value based on the frequency difference, the amplitude difference, and the root-mean-square value; and 
 detecting a cardiac condition based on the value. 
 
     
     
       29. A method to detect a cardiac condition, the method comprising:
 calculating, with a processor, a frequency difference between a first frequency of a first cardiac signal and a second frequency of a second cardiac signal, wherein the first cardiac signal and the second cardiac signal are vibrocardiography signals; 
 calculating, with the processor, an amplitude difference between the first cardiac signal and the second cardiac signal; 
 calculating, with the processor, a root-mean-square value based on a difference between the first cardiac signal and the second cardiac signal; 
 calculating, with the processor, a value based on the frequency difference, the amplitude difference, and the root-mean-square value; 
 detecting a cardiac condition based on the value; and 
 calculating a score based on the value and at least one previously calculated value, wherein the score represents a degree of clinical intervention. 
 
     
     
       30. A method to detect a cardiac condition, the method comprising:
 calculating, with a processor, a frequency difference between a first frequency of a first cardiac signal and a second frequency of a second cardiac signal, wherein the first cardiac signal and the second cardiac signal are vibrocardiography signals; 
 calculating, with the processor, an amplitude difference between the first cardiac signal and the second cardiac signal; 
 calculating, with the processor, a root-mean-square value based on a difference between the first cardiac signal and the second cardiac signal; 
 calculating, with the processor, a value based on the frequency difference, the amplitude difference, and the root-mean-square value; 
 detecting a cardiac condition based on the value; 
 obtaining a first cardiac signal template from a memory; 
 filtering the first cardiac signal based on the first cardiac signal template; 
 identifying a first cardiac event within the filtered first cardiac signal; 
 identifying a second cardiac event within the filtered first cardiac signal; 
 determining a first mean of the cardiac events; 
 temporally aligning the cardiac events based on the first mean and the first cardiac signal template; and 
 determining a second mean of the temporally aligned cardiac events, the second mean being at least part of a second cardiac signal template. 
 
     
     
       31. The method as described in  claim 30 , wherein the first cardiac signal is received via an accelerometer coupled to a patient. 
     
     
       32. The method as described in  claim 30 , wherein a subsequent detection of a cardiac event uses the second cardiac signal template. 
     
     
       33. The method as described in  claim 30 , wherein identifying the first cardiac event comprises receiving an input from a user indicative of the first cardiac event. 
     
     
       34. A method to detect a cardiac condition, the method comprising:
 calculating, with a processor, a frequency difference between a first frequency of a first cardiac signal and a second frequency of a second cardiac signal, wherein the first cardiac signal is indicative of a first breathing phase and the second cardiac signal is indicative of a second breathing phase, wherein the first breathing phase is an expiratory phase and the second breathing phase is an expiratory phase, wherein the first cardiac signal and the second cardiac signal are vibrocardiography signals; 
 calculating, with the processor, an amplitude difference between the first cardiac signal and the second cardiac signal; 
 calculating, with the processor, a root-mean-square value based on a difference between the first cardiac signal and the second cardiac signal; 
 calculating, with the processor, a value based on the frequency difference, the amplitude difference, and the root-mean-square value; and 
 detecting a cardiac condition based on the value. 
 
     
     
       35. A method to detect a cardiac condition, the method comprising:
 calculating, with a processor, a frequency difference between a first frequency of a first cardiac signal and a second frequency of a second cardiac signal, wherein the first cardiac signal and the second cardiac signal are vibrocardiography signals; 
 filtering the first cardiac signal using a band pass filter; 
 calculating, with the processor, an amplitude difference between the first cardiac signal and the second cardiac signal, wherein calculating the amplitude difference comprises calculating a difference between a first amplitude ratio and a second amplitude ratio; 
 calculating, with the processor, a root-mean-square value based on a difference between the first cardiac signal and the second cardiac signal; 
 calculating, with the processor, a value based on the frequency difference, the amplitude difference, and the root-mean-square value; and 
 detecting a cardiac condition based on the value. 
 
     
     
       36. A tangible machine-readable storage medium comprising instructions which, when executed, cause a machine to at least:
 calculate a frequency difference between a first frequency of a first cardiac signal and a second frequency of a second cardiac signal, wherein the first cardiac signal and the second cardiac signal are vibrocardiography signals; 
 calculate an amplitude difference between the first cardiac signal and the second cardiac signal, wherein calculating the amplitude difference comprises calculating a difference between a first amplitude ratio and a second amplitude ratio; 
 calculate a root-mean-square value based on a difference between the first cardiac signal and the second cardiac signal; 
 calculate a value based on the frequency difference, the amplitude difference, and the root-mean-square value; and 
 detect a cardiac condition based on the value. 
 
     
     
       37. The machine-readable storage medium as described in  claim 36 , further comprising instructions which when executed cause the machine to calculate the first amplitude ratio and the second amplitude ratio using respective J, H and I peaks of the respective first and second cardiac signals. 
     
     
       38. The machine-readable storage medium as described in  claim 37 , further comprising instructions which, when executed, cause the machine to at least:
 calculate a first difference between an amplitude of a J peak of the first cardiac signal and an amplitude of an I peak of the first cardiac signal; 
 calculate a second difference between the amplitude of the I peak of the first cardiac signal and an amplitude of an H peak of the first cardiac signal; and 
 divide the first difference by the second difference. 
 
     
     
       39. The machine-readable storage medium as described in  claim 37 , further comprising instructions which, when executed, cause the machine to at least:
 calculate a third difference between an amplitude of a J peak of the second cardiac signal and an amplitude of an I peak of the second cardiac signal; 
 calculate a fourth difference between an amplitude of the I peak of the second cardiac signal and an amplitude of an H peak of the second cardiac signal; and 
 divide the third difference by the fourth difference. 
 
     
     
       40. The machine-readable storage medium as described in  claim 36 , further comprising instructions which, when executed, cause the machine to at least:
 normalize the first cardiac signal by an amplitude of a J peak of the first cardiac signal to form a first normalized cardiac signal; 
 normalize the second cardiac signal by an amplitude of a J peak of the second cardiac signal to form a second normalized cardiac signal; and 
 calculate the root-mean-square value based on the difference between the first cardiac signal and the second cardiac signal by calculating a difference between the first normalized cardiac signal and the second normalized cardiac signal. 
 
     
     
       41. The machine-readable storage medium as described in  claim 36 , further comprising instructions which, when executed, cause the machine to temporally align the first cardiac signal and the second cardiac signal prior to calculating the root-mean-square value. 
     
     
       42. The machine-readable storage medium as described in  claim 41 , wherein temporally aligning the first cardiac signal and the second cardiac signal comprises using a J peak of the first cardiac signal and a J peak of the second cardiac signal. 
     
     
       43. The machine-readable storage medium as described in  claim 36 , further comprising instructions which, when executed, cause the machine to compare the value to a threshold associated with a heart condition. 
     
     
       44. The machine-readable storage medium as described in  claim 36 , wherein the first cardiac signal is indicative of a first breathing phase and the second cardiac signal is indicative of a second breathing phase. 
     
     
       45. The machine-readable storage medium as described in  claim 36 , further comprising instructions which, when executed, cause the machine to at least:
 receive an electrocardiographic signal; and 
 calculate a time difference between a peak of the first cardiac signal and a peak of the electrocardiographic signal. 
 
     
     
       46. The machine-readable storage medium as described in  claim 36 , further comprising instructions which, when executed, cause the machine to at least:
 receive an acoustic signal; and 
 calculate a time difference between a peak of the first cardiac signal and a peak of the acoustic signal. 
 
     
     
       47. A tangible machine-readable storage medium comprising instructions which, when executed, cause a machine to at least:
 calculate a frequency difference between a first frequency of a first cardiac signal and a second frequency of a second cardiac signal, wherein the first cardiac signal and the second cardiac signal are vibrocardiography signals; 
 calculate an amplitude difference between the first cardiac signal and the second cardiac signal; 
 calculate a root-mean-square value based on a difference between the first cardiac signal and the second cardiac signal; 
 calculate a value based on the frequency difference, the amplitude difference, and the root-mean-square value; 
 detect a cardiac condition based on the value; and 
 calculate a score based on the value and at least one previously calculated value, wherein the score represents a degree of clinical intervention. 
 
     
     
       48. A tangible machine-readable storage medium comprising instructions which, when executed, cause a machine to at least:
 receive an electrocardiographic signal; 
 calculate a time difference between a peak of a first cardiac signal and a peak of the electrocardiographic signal; 
 calculate a frequency difference between a first frequency of the first cardiac signal and a second frequency of a second cardiac signal, wherein the first and second cardiac signals are vibrocardiography signals; 
 calculate an amplitude difference between the first cardiac signal and the second cardiac signal; 
 calculate a root-mean-square value based on a difference between the first cardiac signal and the second cardiac signal; 
 calculate a value based on the frequency difference, the amplitude difference, and the root-mean-square value; and 
 detect a cardiac condition based on the value. 
 
     
     
       49. A tangible machine-readable storage medium comprising instructions which, when executed, cause a machine to at least:
 receive an acoustic signal; 
 calculate a time difference between a peak of a first cardiac signal and a peak of the acoustic signal; 
 calculate a frequency difference between a first frequency of the first cardiac signal and a second frequency of a second cardiac signal, wherein the first and second cardiac signals are vibrocardiography signals; 
 calculate an amplitude difference between the first cardiac signal and the second cardiac signal; 
 calculate a root-mean-square value based on a difference between the first cardiac signal and the second cardiac signal; 
 calculate a value based on the frequency difference, the amplitude difference, and the root-mean-square value; and 
 detect a cardiac condition based on the value.

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